Cross-linking of B7-H1 on EBV-transformed B cells induces apoptosis through reactive oxygen species production, JNK signaling activation, and fasL expression.
B7-H1 is a newly identified member of the B7 family with important regulatory functions in cell-mediated immune responses, and it is expressed in human immune cells and several tumors. We first observed that expression of surface B7-H1 on B cells was increased during the immortalization process by EBV, which is strongly related to both inflammation and tumorigenesis. Cross-linking of B7-H1 on EBV-transformed B cells using anti-B7-H1 Ab (clone 130002) induced reactive oxygen species (ROS) generation, mitochondrial disruption, release of apoptotic proteins from mitochondria, and subsequent apoptosis. Inhibition of caspases and ROS generation recovered B7-H1-mediated apoptosis and proteolytic activities of caspase-8, -9, and -3. We observed that B7-H1 stimulation induced both transcription and translation of fasL. ZB4, an antagonistic anti-fas Ab, and NOK-1, an antagonistic anti-fasL Ab, effectively blocked apoptosis without exerting any influence on ROS generation. N-acetylcysteine (NAC) completely blocked the induction of fasL mRNA and protein. We found that B7-H1 stimulation activated the phosphorylation of JNK and c-jun and down-regulated ERK1/2 and p-Akt. NAC blocked the activation of JNK and down-regulation of ERK, but both z-VAD-fmk (N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone) and ZB4 did not inhibit JNK activation of B7-H1 stimulation. SP600125 blocked fasL induction and apoptosis but did not affect ROS generation after B7-H1 stimulation. Taken together, we concluded that B7-H1-mediated apoptosis on EBV-transformed B cells may be involved in the induction of fasL, which is evoked by ROS generation and JNK activation after cross-linking of B7-H1. These results provide a new concept for understanding reverse signaling through B7-H1 and another mechanism of tumor immunotherapy using anti-B7-H1.
Kim
Yeong Seok
YS
Department of Anatomy and Research Center for Tumor Immunology, Inje University College of Medicine, Busan, Republic of Korea.
Park
Ga Bin
GB
Lee
Hyun-Kyung
HK
Song
Hyunkeun
H
Choi
In-Hak
IH
Lee
Wang Jae
WJ
Hur
Dae Young
DY
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D017209:Apoptosis / Q000276:immunology*; D016175:B-Lymphocyte Subsets / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism / Q000821:virology; D018122:B7-1 Antigen / Q000378:metabolism*; D002144:Callithrix; D002461:Cell Line, Transformed; D003432:Cross-Linking Reagents / Q000378:metabolism; D004789:Enzyme Activation / Q000276:immunology; D053222:Fas Ligand Protein / Q000096:biosynthesis* / Q000235:genetics; D004854:Herpesvirus 4, Human / Q000276:immunology*; D006801:Humans; D060945:Inducible T-Cell Co-Stimulator Ligand; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism* / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000276:immunology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation / Q000276:immunology; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D018122:B7-1 Antigen; D003432:Cross-Linking Reagents; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D060945:Inducible T-Cell Co-Stimulator Ligand; D017382:Reactive Oxygen Species; D051057:Proto-Oncogene Proteins c-akt; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3